Press brakes, stamping presses, and drawing presses are examples of some of the machine tools in which the work of the machine is accomplished as an incident to movement of a ram. In the case of most machines of that type, operating power is supplied by a prime mover that is connected to the ram by operation of a clutch mounted upon the frame of the machine. While other kinds of clutches are employed, a slip clutch is frequentyly used which is actuated and released by mechanical movement of its parts. Movement is imparted to those clutch parts through a mechanical operating member the output end of which is connected to the clutch parts and the input end of which is manually moved by the operator's hand or foot. The operating member usually comprises a linkage and lever system. The invention is applicable to the control of slip clutches whether or not the clutch is actuated mechanically or hydraulically or electromagnetically. Use of the slip type clutch facilitates the kind of operation in which the machine ram is moved down in increments, a procedure in which the ram is said to be "floated." In a common arrangement, clutch actuation is accomplished by movement of a foot lever or pedal. In the simplest arrangement, movement of the foot lever is translated by a linkage system directly to the clutch plate. However, that simple system has proven difficult in the past to integrate with operation of safety devices whose purpose is to ensure that the operator is clear of the ram before the ram can be actuated.